mx.kronos.net has no MX records.
Question and response
Question
dig mx.kronos.net. MX
Answer
The response has no answer records.
Authority
kronos.net. 900 SOA ns1-auth.kronos.net. hostmaster.kronos.net. 70421 3600 1800 604800 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0